The fourth prototype of the X-axis CPC (type XLL) was constructed. The apparatus holds a pair of column holders at L/R = 2 where R (7.6cm) is the distance between the holder axis and the central axis of the centrifuge and L (15cm), the lateral disposition of the column holder along the holder axis, this is compared with L/R = 1 in the third prototype (type XL) reported earlier. Using short coils of 2.6mm ID PTFE (polytetrafluoroethylene) tubing with 7.6cm and 24cm helical diameters, retention of the stationary phase was measured in 10 pairs of two-phase solvent systems under various experimental conditions by combining three factors, i.e., the planetary motion (P(l) and P(II)), the head-tail elution mode (H:head to tail;T:tail to head), and the inward-outward elution mode (I:inward;O:outward). The results indicated that a satisfactory retention (over 50%) of the stationary phase is obtained in both diameter coils by choosing the optimum combinations of those three factors. Among the 8 possible combinations, P(I)-T-I and P(Il)-H-l produced the highest retention of the lower phase and P(H)-T-O and P(I)-H-O produced the highest retensor, of the upper phase. Using a simple statistical analysis, the effects of each factor on the stationary phase retention were isolated. The unique hydrodynamic mechanism involved in the present X-axis CPC system was discussed with the aid of the force distribution diagrams obtained from a mathematical analysis of acceleration.